The present invention relates to a method for sealing metal tubes, such as tubes for filling containers for gas at high pressure or evacuation tubes for vacuum vessels.
It is known to seal tubes of malleable metals (for example copper) by simple constriction (pinch) but seals obtained in this manner withstand only modest differences between the internal and external pressures on the tube.
For stainless steel tubes with small internal diameters (about 2 mm at most) it is also known to form the seal by pinching and welding the tube (pinch-weld), possibly after the introduction of a malleable gold wire into the tube to be sealed.
The problem remains of sealing metal tubes with average to large internal diameters and ensuring that a seal is obtained through which losses cannot be detected with a mass-spectrometer leak detector, even at pressures within the tube of up to 20 MPa.